JP2000150709A - Semiconductor package - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor package which is high in bonding strength to a mounting board and excellent in solder jointing reliability when the semiconductor package is mounted on a mounting board by solder joint. SOLUTION: This BGA semiconductor package 50 is equipped with two support poles 52 of shape memory alloy located at the opposed peripheral parts of an interposer board 12. The support pole 52 is extended along the underside of the interposer board 12 at a critical temperature or below, made to protrude downward from the underside of the interposer board 12, and extended at a critical temperature or above. When the semiconductor package 50 is mounted on a mounting board 28, the semiconductor package 50 is mounted on the mounting board 28 at an accurate position first and then heated in an reflow oven to melt the solder balls. While the solder balls are melted, the support poles 52 of shape memory alloy provided to the semiconductor package 50 are made to protrude and extended downward by the heat of the reflow oven. The semiconductor package is pushed up by the support poles 52, so that solder joint 54 is formed like a column or a barrel getting from constriction and becomes excellent in shape where no stress is concentrated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor package mounted on a mounting board by solder bonding, for example, a semiconductor package such as a BGA type semiconductor package or an LGA semiconductor package. The present invention relates to a BGA type semiconductor package or an LGA semiconductor package having a high bonding strength with a substrate and having high solder bonding reliability for a long time.

[0002]

2. Description of the Related Art A BGA type semiconductor package 10 is a semiconductor package of a type developed with an increase in the degree of integration of a semiconductor device. Conventionally, as shown in FIG. The semiconductor device comprises a semiconductor chip 14 bonded to the interposer substrate 12 with an epoxy-based adhesive or the like, and solder balls 18 formed on a plurality of lower electrodes 16 of the interposer substrate 12.

The semiconductor chip 14 has electrode pads 2 on the upper surface.
0, and the electrode pad 20 is
Is connected to the printed wiring 24 on the interposer substrate 12. The semiconductor chip 14 is overmolded with a sealing resin 26 in a bonded state. A large number of lower electrodes 16 provided on the lower surface of the interposer substrate 12
2 and the electrode pads 20 are connected to the circuit of the semiconductor chip 14. A spherical solder ball 18 having a diameter of about の of the electrode pitch is fixed to each lower surface electrode 16.

When the BGA type semiconductor package 10 is mounted on the mounting substrate 28, the semiconductor package 10 is placed on the mounting substrate 28 and is sent to a reflow furnace, where the solder balls 18 are melted and solidified. As shown in FIG. 5B, a solder joint 32 is formed between the lower electrode 16 of the interposer substrate 12 and the electrode 30 of the mounting substrate 28.

[0005] The LGA semiconductor package 40 is a semiconductor package of a type developed in accordance with high integration of a semiconductor device. As shown in FIG. 6B, the interposer substrate 12 made of glass epoxy resin or the like is used. And a semiconductor chip 14 bonded to the interposer substrate 12 with an epoxy-based adhesive or the like, and a lower surface electrode / solder land 42 of the interposer substrate 12. Semiconductor chip 1
4 is similar to the above-mentioned BGA type semiconductor package 10,
An electrode pad 20 is provided on the upper surface, and the electrode pad 20 is connected to a printed wiring 24 on the interposer substrate 12 by a bonding wire 22. The semiconductor chip 14 is overmolded with a sealing resin 26 in a bonded state. A large number of lower surface electrodes and solder lands 42 provided on the lower surface of the interposer substrate 12 are connected to the circuit of the semiconductor chip 14 via the printed wiring 24, the bonding wires 22 and the electrode pads 20.

When mounting the LGA type semiconductor package 40 on the mounting board 28, a solder paste (not shown) is applied to the solder lands 42 of the semiconductor package 40, and then the semiconductor package 40 is placed on the mounting board 28. And send it to the reflow furnace together. Thus, the solder paste is melted and solidified, and as shown in FIG. 6B, the lower surface electrode / solder land 42 of the interposer substrate 12 and the mounting substrate 2
The solder joints 44 are formed between the electrodes 30 and 8.

[0007]

The preferred shape of the solder joint 32 or 44 formed between the lower electrode 16 or the solder land 42 of the interposer substrate 2 and the electrode 30 of the mounting substrate 28 is as shown in FIG. In addition, as described above, the BGA semiconductor package 10 and the LGA mounted in accordance with the current mounting method despite being cylindrical or drum-shaped
As shown in FIG. 5B, the solder joints 32 and 44 formed between the semiconductor package 40 and the mounting board 28
As shown in FIG. 6 (b), it has a flat disk shape. As a result, the stress due to the temperature cycle and the external stress concentrate on the constriction of the solder joints 32 and 44. For this reason, stress or external stress concentrated on the constriction causes a crack in the constriction, and the solder joints 32 and 44 are separated from the interposer substrate 12 and the electrical and mechanical connection with the mounting substrate 28 is broken.

In the case of the LGA semiconductor package 40, due to its structure, as shown in FIG. 6B, the distance between the mounting substrate 28 and the electrode solder lands 42 is short. Stress increases, and there is concern about the strength reliability and life of the solder joint 44.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a BGA type semiconductor package or an LGA semiconductor package which has a high bonding strength with a mounting substrate when mounted by solder bonding and has a long-term high reliability of solder bonding. It is.

[0010]

In order to achieve the above object, a semiconductor package according to the present invention (hereinafter referred to as a first invention) is a semiconductor package mounted on a mounting board by solder bonding. Each of the opposing peripheral edges of the lower surface has a rod-shaped support column made of a shape memory alloy, and the support column extends along the lower surface at a temperature equal to or higher than the transformation point, and has a temperature equal to or higher than the transformation point of the shape memory alloy. Is characterized in that it protrudes and extends downward from the lower surface of the semiconductor package.

Another semiconductor package according to the present invention (hereinafter, referred to as a second invention) is a semiconductor package mounted on a mounting board by solder bonding. And a support pillar in the form of a coil spring made of a shape memory alloy.The support pillar contracts upward from the lower surface of the semiconductor package at a temperature lower than the transformation point of the shape memory alloy, and expands from the lower surface at a temperature higher than the transformation point. It is characterized in that it protrudes downward and extends.

In the semiconductor package according to the first and second aspects of the present invention, preferably, the support pillar is formed of a shape memory alloy whose transformation point is in a temperature range of 190 ° C. to 250 ° C. At the temperature at which the solder paste on the solder land melts, that is, the melting point of eutectic solder, at a temperature of 183 ° C. or higher, for example, 200 ° C., the support column made of a shape memory alloy extends downward or extends downward. Accordingly, the support pillar holds the semiconductor package at a predetermined interval with respect to the mounting substrate. In other words, the support pillar made of shape memory alloy,
By functioning as a spacer for maintaining the distance between the mounting substrate and the semiconductor package at a predetermined size, a solder joint having a good cylindrical or drum-like shape can be formed.
The predetermined dimension is 0.1 mm or more and 2 mm or less. In the present invention, as a shape memory alloy, an Fe-based shape memory alloy, Cu
-Al-Ni alloy, Cu-Zn-Al alloy, Ni-Ti
An alloy, an Au-Cd alloy, or the like can be used.

The present invention can be applied to a semiconductor package of a type which is mounted by soldering by soldering. Preferably, the semiconductor package is a BGA (Ball Grid Allay).
It is applied to a semiconductor package or an LGA (Land Grid Allay) semiconductor package.

After placing the semiconductor package on the printed wiring board on which the solder paste has been printed, the solder is melted in a reflow furnace. At this time, the support column of the shape memory alloy incorporated in the side surface or the inside of the semiconductor package protrudes and expands due to the temperature of the reflow furnace, and serves as the support column to push up the semiconductor package. As a result, the gap between the semiconductor package and the mounting board is forcibly maintained at a predetermined interval, so that the molten solder ball has a cylindrical shape or a drum shape. The cylindrical or drum-shaped solder joints are robust against temperature cycling stress, prolong the solder joint life and improve reliability.

[0015]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. Embodiment 1 This embodiment is an example of the embodiment of the semiconductor package according to the first invention, and FIG. 1A shows the side surface of the semiconductor package at a temperature lower than the transformation point of the shape memory alloy. FIG. 1B is a side view of the semiconductor package in a temperature state equal to or higher than the transformation point of the shape memory alloy, and FIG. 2 is a semiconductor showing a shape of a solder joint when the semiconductor package is soldered on a mounting substrate. It is a side view of a package. The semiconductor package 50 according to the present embodiment is a BGA type semiconductor package mounted on a mounting board by solder bonding.
As shown in (a), in addition to the configuration of the conventional BGA type semiconductor package 10, two opposing peripheral portions 51A and 51B of the interposer substrate 12 are each provided with two rod-shaped support columns 52A made of a shape memory alloy. , B.

In this embodiment, as the shape memory alloy,
An Fe-based shape memory alloy is used. Other than that,
For example, a Cu-Al-Ni alloy, a Cu-Zn-Al alloy, a Ni-Ti alloy, an Au-Cd alloy, or the like can be used. As shown in FIG. 1A, the support pillar 52 extends along the lower surface at a temperature higher than the transformation point of the shape memory alloy, and at a temperature higher than the transformation point, as shown in FIG.
It protrudes downward from the lower surface of the interposer substrate 12 and extends. If, for example, an iron-based shape memory alloy is used as the support pillar 52, the composition is adjusted to 150 ° C. to 300 ° C.
At a temperature at which the transformation point can be freely set between ℃ and the melting point of the eutectic solder, that is, 183 ° C., and the solder is sufficiently melted, for example, at 200 ° C., the support column 52 is attached to the interposer substrate 12. And protrudes downward from the lower surface of the.

When mounting the semiconductor package 50 on a mounting board 28 such as a printed wiring board on which solder paste is printed using a printing machine or the like, first, a component mounting machine or the like is used to place the semiconductor package 50 in an accurate position. The semiconductor package 50 is arranged. Next, the solder balls 18 are melted by heating the mounting board 28 and the semiconductor package 50 together in a reflow furnace. While the solder balls 18 are being melted, the support columns 52 made of a shape memory alloy provided on the semiconductor package 50 by the heat of the reflow furnace protrude and extend downward. The support column 52 pushes the semiconductor package 50 upward with respect to the mounting board 28, thereby forcibly setting the distance between the semiconductor package 50 and the mounting board 28 to a predetermined dimension, for example, 0.1 mm or more and 2 mm or less. The lower electrode 16 of the interposer substrate 12 and the mounting substrate 2 are held.
As shown in FIG. 2, the solder joint 54 formed between the electrode 8 and the electrode 8 is formed in a columnar or drum shape, and has a shape without constriction, that is, a favorable shape in which stress is not concentrated. Next, the semiconductor package 50 is taken out of the reflow furnace and allowed to cool to a temperature below the transformation point of the shape memory alloy.
For example, when the temperature is set to 100 ° C., the support columns 52 again extend in the original form, that is, along the lower surface of the interposer substrate 12, as shown in FIG.

Embodiment 2 This embodiment is an example of an embodiment of a semiconductor package according to the second invention. FIG. 3A shows a semiconductor package at a temperature lower than the transformation point of a shape memory alloy. FIG. 3B is a side view of the semiconductor package at a temperature equal to or higher than the transformation point of the shape memory alloy, and FIG. 4 is a view of a solder joint when the semiconductor package is solder-joined on a mounting board. It is a side view of the semiconductor package which shows a shape. The semiconductor package 60 of the present embodiment is a BGA semiconductor package mounted by soldering. In addition to the configuration of the conventional BGA type semiconductor package 10, as shown in FIG. Are provided with coil spring-shaped support columns 62 made of a shape memory alloy, respectively.

At a temperature equal to or lower than the transformation point of the shape memory alloy, the support column 62 is placed in a cavity 64 having an opening at the lower end and provided downward in the interposer substrate 12, as shown in FIG. It exists in a contracted state and, at a temperature equal to or higher than the transformation point, extends downward from the lower surface of the interposer substrate 12 and protrudes, as shown in FIG. In the present embodiment,
As the shape memory alloy, an Fe-based shape memory alloy is used. Other than that, for example, Cu-Al-Ni alloy,
A Cu-Zn-Al alloy, a Ni-Ti alloy, an Au-Cd alloy, or the like can be used. If an iron-based shape memory alloy is used for the support pillars 14, by adjusting the composition,
Since the transformation point can be set freely between 0 ° C. and 300 ° C., the temperature exceeds the melting point of eutectic solder, that is, 183 ° C., and the temperature at which the solder is sufficiently melted, for example, 200 ° C. , Extending and protruding downward from the cavity 64.

When mounting the semiconductor package 60 on a mounting board 28 such as a printed wiring board on which solder paste has been printed using a printing machine or the like, first, a component mounting machine or the like is used to place the semiconductor package 60 in an accurate position. The semiconductor package 60 is mounted. Next, the solder ball 18 is melted by heating the mounting board 28 and the semiconductor package 60 together in a reflow furnace. While the solder ball 18 is being melted, the support pillar 62 made of a shape memory alloy provided on the semiconductor package 60 is protruded by the heat of the reflow furnace and extends downward. The support column 62 pushes the semiconductor package 60 upward as shown in FIG. 4, thereby forcibly setting the distance between the semiconductor package 60 and the mounting board 28 to a predetermined dimension, for example, 0.1 mm or more and 2 mm or less. The solder joint 66 is formed in a columnar or drum shape, and has a shape without constriction, that is, a good shape in which stress is not concentrated. Next, when the semiconductor package 10 is taken out of the reflow furnace and allowed to cool, and reaches a temperature below the transformation point of the shape memory alloy, for example, 100 ° C., the support pillar 62 contracts again into its original shape, that is, into the cavity 64. .

In the above-described example, the BGA type semiconductor package has been described as an example, but the present invention is naturally applicable to an LGA type semiconductor package.

[0022]

As described above, according to the present invention, the spacing between the semiconductor package and the mounting substrate is forcibly set to a predetermined size, for example, by using the support pillar made of a shape memory alloy as a spacer. It can be kept at 0.1 mm or more and 2 mm or less. As a result, the solder joint can be formed in a columnar or drum shape, and the connection interval can be kept long, so that the solder joint is prevented from being damaged by stress caused by a temperature cycle or the like, and the life of the semiconductor package is reduced. Can be greatly improved.

[Brief description of the drawings]

1A is a side view of a semiconductor package according to a first embodiment, and FIG. 1B is a side view of the semiconductor package at a temperature lower than a transformation point of a shape memory alloy, and FIG. FIG. 4 is a side view of the semiconductor package in a temperature state equal to or higher than the transformation point of the memory alloy.

FIG. 2 is a side view of the semiconductor package showing a shape of a solder joint when the semiconductor package of the first embodiment is solder-joined on a mounting board.

FIG. 3A is a side view of a semiconductor package according to a second embodiment, and FIG. 3B is a side view of the semiconductor package at a temperature lower than a transformation point of a shape memory alloy, and FIG. FIG. 4 is a side view of the semiconductor package in a temperature state equal to or higher than the transformation point of the memory alloy.

FIG. 4 is a side view of the semiconductor package showing a shape of a solder joint when the semiconductor package of the second embodiment is solder-joined on a mounting board.

5 (a) is a side view of a conventional BGA type semiconductor package, and FIG. 5 (b) is a solder joint when the BGA type semiconductor package shown in FIG. 5 (a) is soldered on a mounting substrate. It is a side view of the semiconductor package which shows the shape of a part.

6 (a) is a side view of a conventional LGA type semiconductor package, and FIG. 6 (b) is a solder joint when the LGA type semiconductor package shown in FIG. 6 (a) is soldered on a mounting substrate. It is a side view of the semiconductor package which shows the shape of a part.

FIG. 7 is a schematic view showing a preferred shape of a solder joint.

[Explanation of symbols]

10: conventional BGA type semiconductor package, 12: interposer substrate, 14: semiconductor chip, 16: lower surface electrode, 18: solder ball, 20: electrode pad, 22
... bonding wire, 24 ... printed wiring, 26 ...
Sealing resin, 28 mounting board, 32 electrodes, 32
... Solder joint, 40 ... Conventional LGA type semiconductor package, 42 ... Bottom electrode and solder land, 44 ... Solder joint, 50 ... Semiconductor package of the first embodiment, 51 ...
... peripheral part, 52 ... support pillar, 54 ... solder joint part, 60
... The semiconductor package of the second embodiment, 62... A support column, 64... A cavity, 66.

Claims (5)

[Claims] 1. A semiconductor package to be mounted on a mounting substrate by solder bonding, wherein two opposing peripheral edges of a lower surface of the semiconductor package are provided with rod-shaped support columns made of a shape memory alloy, respectively. At the temperature of extends along the lower surface,
A semiconductor package characterized by protruding downward from the lower surface of a semiconductor package at a temperature equal to or higher than the transformation point of the shape memory alloy. 2. A semiconductor package to be mounted on a mounting board by soldering, wherein two opposing peripheral edges of a lower surface of the semiconductor package are provided with support columns in the form of coil springs made of a shape memory alloy, respectively. A semiconductor package characterized in that it shrinks upward from the lower surface of the semiconductor package at a temperature lower than the transformation point of the alloy, and extends and protrudes downward from the lower surface at a temperature higher than the transformation point. 3. The semiconductor package according to claim 1, wherein a length of the support pillar extending downward from a lower surface of the semiconductor package is 0.1 mm or more and 2 mm or less. 4. The semiconductor package according to claim 1, wherein the support column is formed of a shape memory alloy whose transformation point is in a temperature range of 190 ° C. or more and 250 ° C. or less. 5. The semiconductor package is a BGA (Ball Grid).
Allay) Semiconductor package or LGA (Land Grid Alla)
y) a semiconductor package;
Or the semiconductor package according to 2.